Mars’ underground lakes are made of frozen soil, not water

The ice cap at the South Pole of Mars – © ESA / DLR / FU Berlin / Bill Dunford

New research refutes the idea that lakes of liquid water are buried under the ice cap of Mars’ south pole. Recent experiments suggest that the “water” signal identified a few years ago was more likely to be produced by frozen soil.

a weak theory

While there is a fair amount of evidence pointing to a hazy past for the Red Planet, there is still liquid water accumulating there today, making it a Holy Grail. In 2018, the radar probe returned a signal consistent with the surface of the water Mars Express led the researchers to conclude that a lake of liquid water about twenty km in diameter lay beneath 1.5 km of solid ice, and subsequent observations revealed a full range of them.

But their apparent existence soon raised other questions. To explain the presence of liquid water at such a low temperature, the scientists hypothesized that an eclectic mixture of salts, ” Cap of ice, lowers its freezing point. While other teams suggested that the lake was probably heated by volcanic activity, implying that Planet Mars geologically more active than expected.

Three new research published in the journal geophysical research Letter Defeating this principle. Over the first 15-year period 44,000 radar echoes measured in the region were analyzed and dozens of other similar signals were identified. Many of them have been found too close to the surface for liquid water to exist, even taking into account factors that can lower its freezing point.

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Radar image of bright spots below Mars’ south pole, previously interpreted as evidence of the presence of liquid water – © ESA / NASA / JPL-Caltech

As the lake hypothesis was unlikely, other studies sought to determine the origin of these light signals, and found that they may have been produced by underground soil, metal-rich minerals and salt ice.

concurrent result

In a third study, the researchers put one of these ideas to the test, focusing on a type of soil, called smectites, that formed in the presence of liquid water over long periods of time. The samples were frozen with liquid nitrogen at -50 °C (close to the temperature they would be subject to at the Mars South Pole) and then placed in an instrument measuring their radar reflections.

The correspondence with the observations of the investigation was found to be almost correct. Further evidence was provided by data from the investigation. Mars Reconnaissance Orbiter (MRO), indicating that these smectites were common on the surface of the sphere. Obviously, the studies can’t confirm that smectites are definitely the source of the strange signals, but they put a chill on the theory, offering a more plausible explanation than underground lakes, though less exciting.

« In planetary science, we often only get closer to the truth. The original study didn’t prove it was water, and these new documents don’t prove it isn’t. But we try to narrow down the possibilities as much as possible to reach a consensus », conclusion Jeffrey Platt, lead author of one of the studies.

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About the Author: Tad Fisher

Prone to fits of apathy. Music specialist. Extreme food enthusiast. Amateur problem solver.

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